Just hours after a Microsoft security manager said that the week's updates had patched all in-the-wild threats against Office applications, the company late yesterday acknowledged that another bug in Word is being used by hackers to commandeer computers. On Tuesday, Microsoft released 12 security bulletins with patches for 20 vulnerabilities, including six for Word and one each for PowerPoint and Excel. "All the zero-day [vulnerabilities] in Word and Office were patched Tuesday," Mark Griesi, security program manager for the Microsoft Security Response Center (MSRC), said yesterday.

Griesi said the status of the bugs and their patches -- most of which were being used by cybercriminals in targeted attacks -- was confusing. "Some of that is because in the time since the vulnerabilities began appearing, there were other reports on new zero-days," said Griesi. "But those were not new zero-days." Instead, Microsoft determined that in-the-wild exploits weren't working, or that the bugs being used had already been disclosed. The newest Word flaw fits the first scenario. On Feb. 9, McAfee Inc. researchers said that they had found another unpatched bug in Microsoft Word 2000. That same day, Microsoft reported that its analysis indicated the flaw could only crash the word processor. Such distributed denial of service (DDoS) vulnerabilities are considered less threatening, since they may not let the attacker run his own code on the compromised machine.